Editing Tetrapod (section)

====Carboniferous ====
{{See also|List of Carboniferous tetrapods}}
<!--[[File:Pederpes22small.jpg|thumb|right|230px|''[[Pederpes]]'', 359–345 Ma]]-->
<!--[[File:Crassigyrinus BW.jpg|thumb|right|230px|''[[Crassigyrinus]]'']]-->
<!--[[File:Eryops1DB.jpg|thumb|right|230px|''[[Eryops]]'', ≈295 Ma]]-->[[File:Edops craigi12DB.jpg|thumb|right|230px|''[[Edops]]'' (an early temnospondyl, Late Carboniferous - Early Permian)]]During the early Carboniferous, the number of digits on [[hand]]s and feet of stem-tetrapods became standardized at no more than five, as lineages with more digits died out (exceptions within crown-group tetrapods arose among some secondarily aquatic members). By the very beginning of the Carboniferous,<ref name=":4" /> the stem-tetrapods had radiated into two branches of true ("crown group") tetrapods, one ancestral to modern amphibians and the other ancestral to amniotes. [[Lissamphibia|Modern amphibians]] are most likely derived from the [[temnospondyl]]s, a particularly diverse and long-lasting group of tetrapods. A less popular proposal draws comparisons to the "[[lepospondyl]]s", an eclectic mixture of various small tetrapods, including burrowing, limbless, and other bizarrely-shaped forms. The [[Reptiliomorpha|reptiliomorphs]] (sometimes known as "[[anthracosaur]]s") were the relatives and ancestors of the [[amniote]]s (reptiles, mammals, and kin). The first amniotes are known from the early part of the [[Pennsylvanian (geology)|Late Carboniferous]]. All basal amniotes had a small body size, like many of their contemporaries, though some Carboniferous tetrapods evolved into large crocodile-like predators, informally known as "[[Labyrinthodontia|labyrinthodonts]]".<ref>{{Cite book |url=https://books.google.com/books?id=68urAgAAQBAJ&q=%22Like+the+basal+batrachomorphs%2C+the+basal+reptiliomorphs+were+surprisingly+small%22&pg=PA231 |title=When the Invasion of Land Failed: The Legacy of the Devonian Extinctions |isbn=9780231160568 |access-date=2020-04-25 |archive-date=2020-08-08 |archive-url=https://web.archive.org/web/20200808121720/https://books.google.no/books?id=68urAgAAQBAJ&pg=PA231&dq=%22Like+the+basal+batrachomorphs,+the+basal+reptiliomorphs+were+surprisingly+small%22&hl=no&sa=X&ved=0ahUKEwjD1vvpiIPpAhUNuIsKHVoPCngQ6AEIKjAA#v=onepage&q=%22Like%20the%20basal%20batrachomorphs%2C%20the%20basal%20reptiliomorphs%20were%20surprisingly%20small%22&f=false |url-status=live |last1=George r. Mcghee |first1=Jr |date=12 November 2013 |publisher=Columbia University Press }}</ref><ref>{{Cite book |url=https://books.google.com/books?id=Z0YWn5F9sWkC&q=%22As+in+the+oldest+known+amniotes%2C+it+is+both+very+small+and+highly+ossified%22&pg=PA209 |title=Fins into Limbs: Evolution, Development, and Transformation |isbn=9780226313405 |access-date=2020-04-25 |archive-date=2020-08-09 |archive-url=https://web.archive.org/web/20200809023449/https://books.google.no/books?id=Z0YWn5F9sWkC&pg=PA209&dq=%22As+in+the+oldest+known+amniotes,+it+is+both+very+small+and+highly+ossified%22&hl=no&sa=X&ved=0ahUKEwjh9ZXcjoPpAhVlpIsKHQAlDCQQ6AEIKDAA#v=onepage&q=%22As%20in%20the%20oldest%20known%20amniotes%2C%20it%20is%20both%20very%20small%20and%20highly%20ossified%22&f=false |url-status=live |last1=Hall |first1=Brian K. |date=15 September 2008 |publisher=University of Chicago Press }}</ref> Amphibians must return to water to lay eggs; in contrast, amniote eggs have a membrane ensuring gas exchange out of water and can therefore be laid on land.

Amphibians and amniotes were affected by the [[Carboniferous rainforest collapse]] (CRC), an extinction event that occurred around 307 million years ago. The sudden collapse of a vital ecosystem shifted the diversity and abundance of major groups. Amniotes and temnospondyls in particular were more suited to the new conditions. They invaded new ecological niches and began diversifying their diets to include plants and other tetrapods, previously having been limited to insects and fish.<ref name="SahneyBentonFalconLang2010RainforestCollapse">{{cite journal | author= Sahney, S., Benton, M.J. & Falcon-Lang, H.J. | year=2010 | title= Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica | journal=Geology | doi=10.1130/G31182.1 | volume = 38 | pages = 1079–1082 | issue=12 | bibcode=2010Geo....38.1079S}}</ref>